For help finding your serial number
(if your computer does turn on),
you can copy and paste your serial number from the Apple System Profiler: under the Apple menu, click "About This Mac"; then, in the window that pops up, click "More Info" —
your serial number is in the right-hand pane. If your computer does not turn on,
Apple
has a thorough guide .

If you would rather not provide your full serial number,
we also accept 3-digit or 4-digit model identifiers.
If your serial number is 11 digits (pre-2010), the model ID is the last 3 digits;
if it is 12 digits, it is the last 4 digits.
Please be aware that your full serial numbers are recorded only if we are not able to match it to a computer, for the sole purpose of adding its model ID to our database, after which it is deleted.